Christian Lippka of SUN Microsystems has been working on an Enhanced Graphic Export extension for Draw, and has released a beta version for comment.
Note it is BETA but if you would like to check it out you can find details and a link to the binary in the Issue tracking system:
http://www.openoffice.org/issues/show_bug.cgi?id=4499
I have been using it now for a week or so, mostly for screen shots, and it really is quite nice.
Once installed it has no added UI under Draw, until you select 'File>Export', after you name your export file and click "Save" then the dialog opens, based on the type of file format selected for the image.
TIP - the export is for the entire current page. So the way I use it is to capture the screen or a window, dialog to the clip board. Open Draw and paste this to the page. Then I select Original Size for the pasted image and follow that by useing 'Format>Page' to match the size of the graphic. This way when the export is run I get just the image...if I am adding annotations, I do that before the resize, group the items and size the page to the overall group size.
The features in Draw to annotate screen shots and this extension work together to produce one very nice tool for making this type of graphic
Keep an eye out for it at the extensions site.